My opinion is literally only the first sentence. Outside of that is all kinda common sense if you did any reading on the lore that you see on the univers page. I used shyvanna's lore as the example. Its pretty easy to inference how a society is generally structured when you add together a combination of viewpoints.
Im curious as to why you think marriage means that the a person will change what they are. Being married literally only means that two people are tied together and society now views two people as together. Marriage does not define a person and therefore does nothing to the other aspects of said person. The best duelist would still be the best one.
Duels were held for a variety of reasons amongst the nobility. Sometimes even business contracts would lead to duels because things like house x and house y want an exclusive business deal with the same business.
We also don't know how said duels would be handled. Would they be 1 on 1 competitions and single elimination or would there be say two teams and each team sends out 1 fighter at a time and the team with people standing at the end wins.
Let's be honest. In a world where magic exists and both genders can potentially harness said magic do you think it would be prudent to not say something along the lines of hey you lady you're going to marry this guy because you're a woman and you have no say in who you marry. Im certain that things in said magical land where there is zero actual power difference between genders (because magic) would be done differently than here